1. Field Of the Invention
The present invention relates generally to disc brake assemblies for vehicles and, more specifically, to a rotor for a disc brake assembly for use in vehicles as well as a method for making same.
2. Description Of the Related Art
It is known to commonly employ brakes such as disc brakes in vehicles such as automotive vehicles for slowing and stopping the vehicle. Generally, a disc brake assembly includes a disc brake rotor mounted on a wheel hub which rotates with a wheel and a disc brake caliper which is fixedly mounted by fasteners on a wheel spindle of the vehicle. The caliper includes one or more brake shoes or pads movably mounted thereto and adapted to apply braking pressure to one or both sides of the rotor, thereby braking the wheel along which it rotates.
Preferably, the rotors are machined such that the thickness of the rotor is constant throughout its cross section. For example, and as shown in a plan view of a portion of a prior art rotor 10 in FIG. 1, such rotors 10 typically include grooves 12 cut into one or both surfaces of the rotor 10. More specifically, and as known in the art, a single continuous groove 12 is typically spirally cut on a braking or friction surface of the rotor 10 such that the groove 12 appears as a series of grooves cut concentrically about a hub 14 of the rotor 10 and spaced radially equally relative to each other.
One disadvantage of the above prior art rotor when used in a disc brake assembly is that sometimes an unacceptable clack, thump or click type noise (hereinafter referred to as "clack" or "clacking") may occur with the application of the disc brakes. Clack may occur when the brake pad is applied against the friction surface of the rotor 10. The brake pad moves along or follows the path of the groove 12 and, when it reaches the end or stops, the brake pad pops up and slides radially back to repeat itself.
Attempts have been made in the prior art to eliminate "clack". For example, opposed spiral grooves have been employed on opposite sides of the rotor. That is to say, on one side of the rotor, the groove 12 has been cut by a cutting tool moving at a constant feed rate from a point near the hub 14 of the rotor 10 and spiraled outwardly to a radial edge 16 of the rotor 10. On the opposite side, the groove 12 has been similarly cut but beginning from the radial edge 16 of the rotor 10 and moving at a constant feed rate toward the hub 14. The radial spacing of the adjacent grooves 12 in side-by-side relation was essentially equal or constant. However, even after such steps were taken, clacking was not totally eliminated.
Further, an attempt to employ an interrupted groove rather than a continuous groove on one or both sides of the rotor was also found to be unsatisfactory. The interrupted groove was formed by a cutting tool moving at a constant feed rate with a pause at various intervals. The interrupted groove unacceptably increased the cost of manufacturing the rotor and resulted in a shorter useful life of the cutting tool.